1. Field of the Invention
Implementations of various technologies described herein generally relate to the packaging or housing of various sources, sensors and electronics for use inside a wellbore.
2. Background of the Invention
The methodology of housing or packaging sources, sensors, electronics, and general components has seen many changes as technologies and materials have improved over time. In the oil and gas industry, subsurface formations are typically probed by well logging instruments to determine the formation characteristics. Data is typically acquired using sources and sensors disposed on a downhole tool and either stored in downhole memory or transmitted to the surface. As used herein, the term “transducers” is understood to encompass devices capable of operation as sources and/or sensors, and is not to be limited to any one particular signal type (i.e., acoustic, gravity, electromagnetic, pressure, etc.).
In conventional logging operations, particularly in wireline applications, the transducers are often placed on the downhole tool such that they are exposed to the subsurface environment. In some implementations the transducers are mounted within a tool housing filled with a fluid, such as oil. A drawback with this methodology is that such implementations may require volume compensation for the oil. Such mechanisms often entail pistons or bellows that move in response to displacement of the oil as a result of pressure and temperature changes. Further, certain compensating components exposed to the downhole environment may need to be cleaned in between downhole trips to ensure that they function properly. Such mechanisms also increase the mechanical complexity of the system.
However, in logging while drilling (LWD) or measuring while drilling (MWD) applications, the above methodology is not particularly suitable or reliable due to the harsh drilling environment, which may be characterized by high shock conditions, high pressures and high temperatures. Consequently, the transducers and associated electronics are typically disposed inside the drill string and are thereby isolated from the harsh drilling environment, which is detrimental to their ability to serve their intended purposes.
Additionally, when employing acoustic arrays on LWD tools, the conventional approach of having a through-hole in the collar for mounting each transmitter, and each receiver, create certain challenges. For example, the conventional approach greatly limits the sensor spacing distances and the sensor angles. Also, with the conventional approach, tool mechanical-integrity (through bending and pressure) must be maintained and this places added limitations on sensor geometries.
A need remains for improved techniques to package and house transducers and electronics for subsurface use.